In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention.
Tools of the above-related kind are used to ream holes in metallic workpieces by chip removing or cutting machining with the purpose of giving the holes a cylindrical, smooth surface of a certain diameter. A product, which advantageously can be machined by means of the tool, is tube blanks, the interior of which for different reasons has to be dimensionally accurate and have a high surface smoothness. A usual method for, in practice, carrying out machining of just tube blanks is so-called pull boring. The tool is then connected with one end of a bar or long narrow carrier, which has an outer diameter that is smaller than the inner diameter of the tube blank, and which in a first step is brought through the tube blank so that the tool can be applied on the free end thereof, e.g. via a threaded joint, after which the reaming operation is undertaken by a combination of rectilinear and rotary relative motions between the tool and the tube blank. In just pull boring, the tool is fed longitudinally by being pulled through the interior of the tube blank without rotating, at the same time as the tube blank is brought to rotate without longitudinal feed. By these relative motions, the cutting inserts detachably mounted on the tool head will, in a way characteristic of cutting machining, remove chips from the hole wall while generating a cylinder surface having good dimensional accuracy and surface smoothness.
Although the present reaming method usually is reliable and well functioning, at times mishaps occur requiring that the machining operation is interrupted and that the tool is retracted out of the interior of the tube blank. Examples of mishaps are that one or more cutting inserts become damaged or come loose from the tool head, or that the driving machine facility stops. In connection with such interruptions, previously (commercially) known reaming tools may give rise to problems. Accordingly, the intact cutting inserts of the tool head can be jammed against the interior of the tube blank, wherein the cutting inserts are subjected to a reverse interaction of forces that tends to dislodge the cutting inserts out of their predetermined, accurately defined locations in the seats of the tool head. Instead of being held pressed automatically against above all the axial support surface, but also the tangential support surface, by the cutting forces during operation, the cutting insert is subjected to an aim to be dislodged out of the seat. Irrespective of whether the clamping member in question is a screw or a clamp/wedge, this has poor chances of withstanding the reversed forces. Characteristic of a screw is, in this connection, that it has good tensile strength, but considerably inferior bending strength. Particularly if the tool has a moderate diameter and the cutting inserts as well as the screws are relatively small, therefore, it often occurs that the screws yield to the unpredicted, reversed forces that are applied from the cutting insert.